Schroedinger's Cat

What happens if we designed an experiment where a quantum event would have a direct impact on a large object like…a cat!

Imagine a sealed container, so perfectly constructed that no physical influence can pass either inwards or outwards across its walls. With the cat inside the container, there is also a device that can be triggered by some quantum event. The quantum event is the triggering of a photocell by a photon, where the photon had been emitted by some light source, and then reflected off a half-silvered mirror. The reflection at the mirror splits the photon quantum state (wave function) into two separate parts, one of which is reflected and the other is transmitted through the mirror. The reflected part of the photon wave function is focused on the photocell, so if the photons are registered by the photocell, it has been reflected .In that case, the cyanide is released and the cat is killed. If the photocell doesn't register, the photon was transmitted through the half-silvered mirror to the wall behind, and the cat is safe.

Now, let us take the viewpoint of the physicist outside the container. According to the outside observer, no "measurement" has actually taken place, so the quantum state of the entire system is nothing but a linear superposition between alternatives right up to the scale of the cat (Schrödinger equation). Both alternatives must be present in the state.
So, according to the outside observer, the cat is in a linear superposition of being dead and alive at the same time!